h1, h2, h3 {
  margin-top: 0;
}

.header {
  padding: 4em 0 3em;
  background-color: brown;
}

.header-title {
  margin: 0;
  color: white;
  font-size: 4em;
  line-height: 1;
}

.nav {
  position: sticky;
  top: 0;
  margin-bottom: 2em;
  padding: 1em 0;
  background-color: black;
  color: white;
}

.center {
  max-width: 940px;
  margin: auto;
  padding: 0 2em;
}

@media (min-width: 40em) {
  .sidebar {
    position: sticky;
    top: 82px;
    float: right;
    width: 11em;
  }
  .content {
    margin-right: 15em;
  }
}